Details
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Task
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Status: Closed
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Major
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Resolution: Done
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6.5.0, 6.5.1, 6.6.0, 6.5.2
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1
Description
During qualification testing of 6.6.0 it was noted that memcached stats hash detail has a sizeable impact on server performance (ops/s).
The exact cause of that slowdown has not been confirmed, but the belief is that given "hash" must traverse every item in each vBucket's HashTable and (while under lock) accumulate various stats including histograms of chain depth :-
class HashTableDepthStatVisitor : public HashTableDepthVisitor { |
public: |
void visit(int bucket, int depth, size_t mem) { |
(void)bucket; |
// -1 is a special case for min. If there's a value other than |
// -1, we prefer that. |
min = std::min(min == -1 ? depth : min, depth);
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max = std::max(max, depth);
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depthHisto.add(depth);
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size += depth;
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memUsed += mem;
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}
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While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments.
Attachments
Issue Links
Activity
| Field | Original Value | New Value |
|---|---|---|
| Link | This issue relates to CBSE-9027 [ CBSE-9027 ] |
| Component/s | couchbase-bucket [ 10173 ] | |
| Component/s | ns_server [ 10019 ] | |
| Assignee | Daniel Owen [ owend ] |
| Assignee | Daniel Owen [ owend ] | James Harrison [ james.harrison ] |
| Fix Version/s | 6.6.1 [ 17002 ] |
| Link | This issue blocks MB-41023 [ MB-41023 ] |
| Link | This issue blocks MB-40528 [ MB-40528 ] |
| Labels | approved-for-6.6.1 |
| Resolution | Done [ 6 ] | |
| Status | Open [ 1 ] | Resolved [ 5 ] |
| Status | Resolved [ 5 ] | Closed [ 6 ] |
| Resolution | Done [ 6 ] | |
| Status | Closed [ 6 ] | Reopened [ 4 ] |
| Resolution | Done [ 6 ] | |
| Status | Reopened [ 4 ] | Resolved [ 5 ] |
| Assignee | James Harrison [ james.harrison ] | Daniel Owen [ owend ] |
| Status | Resolved [ 5 ] | Closed [ 6 ] |
| Description | {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s). While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments. |
During qualification testing of 6.6.0 it was noted that {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s). The exact cause of that slowdown has not bee
While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments. |
| Description |
During qualification testing of 6.6.0 it was noted that {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s). The exact cause of that slowdown has not bee
While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments. |
During qualification testing of 6.6.0 it was noted that {{memcached stats hash detail}} has a sizeable impact on server performance (ops/s).
The exact cause of that slowdown has not been confirmed, but the belief is that given "hash" must traverse every item in each vBucket's HashTable and (while under lock) accumulate various stats including histograms of chain depth :- {code:c++} class HashTableDepthStatVisitor : public HashTableDepthVisitor { public: void visit(int bucket, int depth, size_t mem) { (void)bucket; // -1 is a special case for min. If there's a value other than // -1, we prefer that. min = std::min(min == -1 ? depth : min, depth); max = std::max(max, depth); depthHisto.add(depth); size += depth; memUsed += mem; } {code} While this is being investigated and improved, temporarily remove this stat call from cbcollect to avoid impacting normal operation in customer environments. |
| Affects Version/s | 6.5.2 [ 17223 ] | |
| Affects Version/s | 6.5.1 [ 16622 ] | |
| Affects Version/s | 6.5.0 [ 15037 ] |
| Remote Link | This issue links to "Slack Discussion (Web Link)" [ 23417 ] |
| Link | This issue relates to CBSE-10992 [ CBSE-10992 ] |